If you find/replace text with itself Word will report the number of hits.
For example, suppose I'm looking for the number of times that "ABcd" (case
specific) occurs in a file. I can do Find/Replace:

Find: ABcd

Replace with: ABcd

Match case enabled

Replace All

Word will tell you how many it replaced, effectively not changing anything.

If case isn't important, then use ^& as the Replace with: string. ^& is the
special match string for "whatever matched the search". Hence, in this case,
if Word found AbCd or ABCD it would replace it with AbCd or ABCD,
respectively.