Redact multiple partial phone numbers

I have a pdf spreadsheet which contains thousands of lines of data including phone numbers.

I need to redact the phone numbers to show only the last 6 characters.

Its fairly easy to find and redact partial words but you have to search individually for each phone number and I have circa 600 unique numbers to redact so one at a time is not practical.

I can also find and redact multiple words at once but it will only redact the entire phone number and won't allow me to leave the last six characters showing.

Any help would be much appreciated.