If you want to find sequences of hex digits (A-F, a-f and 0-9) in a search, you can hack together something like:

/[A-Fa-f0-9]\+

This is a bit verbose, though. Vim has a number of built in character classes that can be referenced in searches and substitutions. For hex digits, there is \x. Using this, the search above can be achieved with:

/\x\+

See :h \x for more details and other character classes.