Cardi B does not play about her money! The rapper told fans she had her credit card stolen ... but she says she knows who did it and is definitely going to make them pay.

According to the "Bodak Yellow" artist ... she recently discovered her AMEX card was missing, but shrugged it off -- until she noticed a purchase on her account for about $40K at Saks Fifth Avenue.

What's weirder ... a purchase for about $20K popped up from the Apple store! At that point, she KNEW something was up ... and so did her accountant. Watch the full clip for the breakdown.

Now, Cardi says whoever took her American Express card is out free on borrowed time ... because she knows what they look like, and she's not about to let them get away with her dough.

She said, bluntly, "Y'all going to jail! I got clear pictures of you motherf***ers."

The video is hilarious ... Cardi breaks down exactly what the suspects look like, giving the locations the pics were taken along with a read of their appearances.

"You're lucky that I don't got your address," she said.

Get 'em Cardi!