How to read all strings of a certain length into shell variables named sequentially?

I was wondering if there was code to find every string of a certain length in a text file and save each one as a new variable? For example, there are 5 strings in a text file. Two of them are 3 characters long. The idea is to parse out all the strings which are 8 characters long and put them in variables going in sequential order, e.g. var1, var2, var3. How would I make this? Thanks! (For those wondering, I found an old file on my PC with a bunch of bitcoin wallets with private keys, trying to save them all as variables to check their balances.)
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