Normally the only way to reverse a MD5 or SHA1 hash back to plain text is via brute force guessing. But there is actually a somewhat easier way that might work for you.

Head over to md5.rednoize.com/, enter your hash, and maybe it'll turn up in the search results. The site has a database of 49,313,614 hashes along with their plain text equivalents, which can reduce your brute force guessing time to nearly zero if your hash happens to already be in their database.