Mr Rock told you right.
9x17 = 380Auto (aka 380ACP and 9mm kurz)
9x18 = Russian "9mm" Makarov
9x19 = Luger (aka ParaBellum)
9x18 isn't really even 9mm as we know it (0.355"). It's really 9.2mm so you can get in trouble really fast with the wrong cartridge in the chamber.
For low budget reloading purposes you can trim down 9x19 brass, then size and load them with Makarov dies. Berry still makes 95gr bullets for reloading. W231 (aka HP-38) works really well.
https://www.berrysmfg.com/product/bp-9x18-mak-364-95gr-rn9mm Makarov went through a heyday in the 1990's when all the Russian and Eastern Blok nations dumped their 9x18 police pistols on the US market. There were more sources back then, but lots of them have now dried up. At one time Sierra and Hornady also made bullets.
Hope this helps.