I am trying to replace {MERGEFIELD Address_3} and {MERGEFIELD "Postal"} with {MERGEFIELD City_state_zip}

Can anyone help me with this?

You don't need a macro for that. All you need is Find/Replace!

Ordinarily the field codes for those would look like:
{ MERGEFIELD Address_3 } and { MERGEFIELD "Postal" }
with a single space character before 'MERGEFIELD'. Assuming that is the case, use Alt-F9 to display the field codes, then do a Find/Replace for
Find = Address_3
Replace = City_state_zip
Find = ^d MERGEFIELD "Postal"
Replace = nothing

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]

Thank you! I feel like quite the idiot, because it is so simple.