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This really depends on how you plan on making your knife, and more to the point, what equipment you have. If you have access to a belt grinder, you can use them as is. They're in the 64HRC range, which is a little hard. If you want to bring them down to 60-61 so they're a little easier to grind and make a tough blade out of them, temper in that 400f-450f range. 2 hours 2 times is plenty. No hotter than 450f.
Now if you have access to a heat treat kiln, another route to take is to take the files as received and "temper" them at 1200f for 2 hours, one time. This we call a "bladesmith's" anneal, and it spheroidizes the steel making it butter butter soft to drill/grind/ etc. The problem with heating up to critical and allowing it to air cool, because files have extra carbon in them past the eutectoid point, the air cool will soften the file, but the resulting structure is known as lamellar pearlite. This structure has alternating sheets of soft, hard, soft, hard, soft, hard. Easy to grind, not so easy to drill or machine. The "bladesmiths" anneal is so much better, IF you have the ability to do it.
Regardless of the anneal you use, it will need to be re-hardened and tempered. So if you don't have the equipment to do any heat treating, the best approach is probably to go ahead and temper it ~400f-450f, and grind away. Good luck!
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