How to search and replace this odd phrase

[sasquatchjimmy]

I’m trying to search and replace a series of characters and numbers

[JohnSUN]

[Villeroy]

\[[:alnum:]{3}\]
A literal [ followed by 3 alphanumerics and a literal ]

[sasquatchjimmy]

Thank you so much!

[sasquatchjimmy]

Thank you so much! I really appreciate it.