You could try a wildcard Find/Replace, where:
Find = <[A-Z ]{1,}[0-9]{2,3} MI[!^13]@^13
Replace = ^&
with the replacement font set to bold. However, it would be better to use a suitably-defined paragraph Style (e.g. a Heading Style) for the replacement instead of simply formatting the replacement as bold. Aside from making the document easier to maintain and less susceptible to corruption, it would also facilitate the creation of a Table of Contents.

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