First of all welcome to the forum.
Without more details, your gun is probably a .38 M&P shipped between 1948 and 1951
Guns made previous to 1957 do not have a Model Designation. Odds are it is a "pre Model 10" of some flavor
Unless it says Model ** on the frame under the cylinder yoke, the numbers are merely assembly numbers and mean nothing.
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If you can give us more details or a picture, we can narrow things down a bit.
No, you shouldn't shoot +P ammo in it.