ST. LOUIS — The Gateway Arch and the postseason are beckoning.

For all the setbacks, injuries and mistakes that have been made, if the 62-62 Mets take care of business these next 38 games — they can make it back to the postseason.

Call this the .38 Special. Back to Paradise.

It’s going to take more than Yoenis Cespedes, but it can be done. The Mets cannot waste another game and must build off their two straight wins over the Giants, one of the wild-card teams in front of them. All that starts Tuesday night against the Cardinals.

The Mets trail the Cardinals by 4 ¹/₂ games and have to jump over two other teams as well, the Marlins and Pirates. They all have flaws.

Here is The Post’s Five-Point Plan back to the postseason.

1. You Go, Yo

Cespedes carried the Mets to the NL East title last season. This year he needs to carry them to the wild card after returning Friday from a quad injury. Already he has lifted the spirits of the team, crushing three monster home runs in the last two wins against the Giants. Leave him in the three-spot and in left field.

Jose Reyes put it perfectly: “Every time I see him go to home plate, I feel like he is going to hit a home run. I think everybody on the team feels the same way. It’s a good feeling to have.’’

2. The Gift Schedule

Of those final 38 games, 22 come against the Twins (3), Reds (3), Braves (6) and Phillies (10) — all of which entered Monday at least nine games under .500. Terry Collins’ Mets can’t take anyone for granted. Collins made that clear, saying, “Every series is big, you have to grind every single one of these out.’’

Thirteen of the final 16 come against the Twins, Braves and Phillies, with the first 10 of those at home. Then comes a three-game series in Miami. Seven of the final 38 games are against the Marlins.

3. Hammer of Thor

Noah Syndergaard is the Mets’ pitching horse. Sunday night was most encouraging, not only because of the eight shutout innings, but because Syndergaard showed real maturity coming out of the game, telling Collins he was gassed.

When you throw the fastest fastball (98.0), the fastest slider (90.8) and the fastest changeup (89.9) in the game among starting pitchers, according to FanGraphs, that can happen. To recognize not to be hero with a shutout — as Matt Harvey tried to be in the World Series — and turn it over to Jeurys Familia shows leadership and teamwork.

4. The Right J.B. and Other New/Old Parts

Jay Bruce has to produce. He can’t be Jason Bay. Some of his struggles since coming to the Mets is hitting into tough luck and some of it is just trying too hard. Bruce insists his swing feels just fine.

“Not once have I felt out of control, like I’m struggling,’’ Bruce said. “My results are not there right now but we have (38) games left.’’

Reyes is coming around at leadoff and was hitting .400 over the previous seven games before going hitless Sunday. Another Prodigal Met, Jon Niese, has a huge assignment Tuesday night starting against Jamie Garcia. He can’t falter. Then on Wednesday, Jacob DeGrom must bounce back from the worst start of his career.

5. Lockdown Bullpen

Because of the weakened rotation with Steven Matz’s shoulder issue, the bullpen is more important than ever. Some of those arms are dragging. Hansel Robles does not have command and lefty Jerry Blevins has tightness in his forearm. That tightness could explain why Blevins has been throwing too many fastballs lately and not enough curve balls.

Will Jim Henderson’s shoulder scream out in pain again before the end of the season or can he survive? Addison Reed needs to be a workhorse and the tight-rope-walking Familia must continue to excel. Familia is as relaxed as ever and pulled the old practical joke of placing real-looking rubber doggie doo on the clubhouse floor before Sunday night’s game. This pen can’t stink it up if the Mets are to pull off this wild-card miracle.

There is the blueprint, let’s see if the Mets can do something special these last 38 games.