In general, Type 1 PostScript fonts don't have file extensions. Most of them look like this:
Adobe Garamond
AGarBol
AGarBolIta
AGarIta
AGarReg
AGarSem
AGarSemIta
The bold, italic name is the suitcase of screen fonts. The rest are the vector outline fonts for printing. How many outline fonts you have for a set simply depends on how many they made. It could be one, it could be 20. But each outline will have at least one matching screen font in the suitcase, or that typeface won't work.
The only place you'll normally see extensions on T1 PS fonts will be for the screen font suitcase. Such as .bmap, .scr and a few others. It's there for no reason other than for the user to easily see which one of the set is the suitcase of screen fonts. The OS doesn't care if the extension is there or not.
As far as converting, you don't need the screen fonts. Everything a converter would need is in the outline fonts.
There are numerous online sites that will convert fonts for free. You upload a handful at a time (usually no more than 5). It converts them and gives you a link to download the converted fonts.
But since you have a lot, this would take a very tediously long time to do. You'd be better off purchasing an app dedicated to doing batch conversions:
https://www.fontlab.com/font-converter/transtype/
https://fontgear.com/products/fontxchange-for-macintosh
