Change owner for all files owned by x
I copyied files from my MacBook, mainly files from /usr.
The one and only user on my computer is called 'Julian' (like on my MacBook).
A lot of the copied files are now owned by '501' (id of "Julian" from the MB). 

    drwxrwxr-x@  28 501     admin   952  8 Jul 23:02 man/

Is there a way to change the owner of all files owned by '501' to 'Julian'?
Change owner for all files owned by x
===

I copyied files from my MacBook, mainly files from /usr.
The one and only user on my computer is called 'Julian' (like on my MacBook).
A lot of the copied files are now owned by '501' (id of "Julian" from the MB). 

    drwxrwxr-x@  28 501     admin   952  8 Jul 23:02 man/

Is there a way to change the owner of all files owned by '501' to 'Julian'?