In the Find & Replace dialogue, tick the "Entire cells" option and search for "7". This will find cells with the numeric value 7, even if displayed as "7", "07", 007" etc., but will not find 17 or 72.
Alternatively, you should ask yourself whether you really need numbers here (so that you can calculate using them) or perhaps instead identifiers that just happen to be made up of digits. If the latter, you would be better (as has already been suggested) having your values as text. With the text string "07" in a cell, you can easily search for "07".
Note that digit strings are not always numbers:
o The Zip code for City Hall in Boston, USA, is 02201; that's not two thousand two hundred and one, nor can you write it "2201" or "2,201" or "002201". What does it mean if the Zip code for one location is the sum of the codes for two others? (Answer: nothing!)
o My telephone area code (here in London, UK) is "020"; that's not twenty.
o If your (unwise) PIN was set as "0987", you could not get money out of an ATM using "987" or "00987". Nor do you get more money by having a "larger" PIN.
o James Bond was not Agent Seven.
I trust this helps.
Brian Barker