Your document's content is nothing like what you described in your post!

Your post describes sentences terminate by periods, with a number immediately following and a space between that and the following text.

Your document has non-breaking spaces instead of periods and no spaces between the numbers and the following text.

How you could expect a working solution when your problem description is so far off the mark is a mystery.


For the document you have attached, you can do this with a wildcard Find/Replace, where:
Find = ^s([0-9]@[A-Z])
Replace = .^l\1

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