Well - first you need a known working 5.25-inch floppy drive. These aren't easy to find nowadays; you also need to know what the sides and density the floppies are: Most will be double-sided, and either double-density or high-density; abbreviated DS/DD or DS/HD - but sometimes you'll find for older 5.25 floppies will be Single Sided/Double Density (SS/DD) - there was also a "single sided/single density", but likely your floppies aren't that.

Back in the day, many of the "SS/DD" floppies were "DS/DD" manufacturing "rejects" that didn't pass QA quality checks - they sold special punches (or you could DIY it with scissors or a hole punch) to cut the proper notch for the timing hole to allow you to format and use the "other side". This was cheaper than buying the ones that passed (a pack of ten floppies could run $20.00 or more, depending on the brand).

If your drive was single sided (meaning it only had one read/write head on one side of the mechanism), you'd have to flip the floppy over (aka - a "flippy"/"flippie") - but then the media would be rotating backwards relative to the "good" side; any dirt that the cleaning wipes on the inside of the main "jacket" in theory could become dislodged and cause problems, but I never encountered that as a kid. But it was a concern at the time. The price difference though made it an acceptable tradeoff.

Of course, after getting a working floppy drive, you'd then need a way to hook it up; if you have a motherboard that still has floppy connectors, and you have a cable, then you're one step closer. Otherwise you'll have to use a more complex solution (like the mentioned KryoFlux board).

But getting that floppy drive is the first step; if you can, get at least a DS/DD drive minimum; if you can get both a DS/DD and DS/HD drive, that's a good thing too. Otherwise, if all you can find is the DS/HD drives, better than nothing. In theory, a DS/HD drive can read anything (backwards compatible), but in practice by people doing these kinds of recovery, that hasn't always worked out, whereas getting the drive to match the floppy is the better solution.

Finding these drives can be problematic, mainly because of a variety of reasons. There's the whole "vintage PC" movement and crowd which have been driving up prices and causing problems with finding the parts, but the greater problem (for virtually anything pre-486) has been manufacturing: Many factories and whatnot used a variety of machine tools which used an "embedded" PC - usually a 286 or 386 - for CNC and similar control work. So finding working floppy drives, not to mention motherboards - has been a pain; as this was becoming known, too, prices have escalated.

You'll also probably find that a lot of older PC parts - for some reason, at least on ebay - are being listed out of former Eastern European countries; I am not sure why that is, or how legit it is. You'll also find a lot of stuff from China - again, I don't know the legitimacy of those offers. It may have been one of those "dumping ground" things for PC recyclers here in the USA; if you are based in the USA, it would be best to only look for parts from the USA, alternatively check Craigslist, and local area hamfests for old computer parts.