There's a list of free and paid SWF decompilers nicely aggregated on a single page: http://bruce-lab.blogspot.com/2010/08/freeswfdecompilers.html?m=1

There's also a stack overflow question about it with more tools at https://stackoverflow.com/questions/97018/how-do-you-decompile-a-swf-file

Some more stuff I found from a google search:

https://www.flash-decompiler.com/
https://github.com/jindrapetrik/jpexs-decompiler

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But I think the bigger question here is what kind of wallet it is? All wallet softwares put a special sequence of bytes at the beginning of the wallet file that uniquely identifies its type (the so-called Magic Bytes).

Install a hex editor such as HxD (and make a copy of the extracted wallet file because HxD allows you to unintentionally edit and save the file just by typing keys on the keyboard!) and open the wallet file with it, look at the first 10 or so bytes and see if they match any of the defined magic bytes.