Zastava M70 .32 ACP 3.7" Barrel 8 Rnd Blued Refurbished - $209.85

My ex whore GF went into church... sounded like bacon sizzling

The rear sight is a plastic POS, and your groups will literally be 2 feet high @10 yards. The gun itself is not much better. I made the mistake of buying one and had to do a lot of work to it just to make it function reliably. Also, make sure you have some good shooting gloves as the trigger is sharp and has a 10+ pound pull. The chamber on mine is so oversized, it will ruin brass in no time so if you're a reloader, as I am, forget it. I'm saving it for the next buyback to recoup my money.

It says 'Refurbished'.
It didn't say it was a high quality refurb.....dig ?
Some schmo had a spare sitting on the shelf and guess what ? it fit....kinda....almost....sorta.....not at all.

Assuming the mag well is large enough to accommodate a 9mm/380 magazine, you will need to rebarrel it. Then, either checking if they made a 380 version and get it or ordering a blank and having it machined to fit it. And then getting stiffer recoil spring and possibly adding weight to the slide because this is a blowback pistol (no idea of specs; some clever people probably can figure it out). If you have to pay someone to do it, by the time you are done you have added at least $300-400 to the pistol.

You would be better off getting a Makarov pistol: all you would need is replacing the barrel and finding 380 Makarov barrels is not that hard. All you then need is remove old barrel, press new one until it is properly headspace, drill hole for pin, insert pin, and off you go. Total cost will be less than $500 but not by far though

If your goal on doing this was to save a buck or two, I think you may want to reconsider. You can buy pretty decent pistols in 380 or 9mm caliber with $500 even today.