Custom Formatting Number to Text

Here is the situation, I have a spreadsheet with data that was downloaded from one of our legacy systems. The format of the owner ID is #####, however, coming out of the legacy system it is text. I have pulled our owner information from SQL from our current database, when it comes out of the current database it is stored as a number and is not following the ##### format. for example, in the legacy system, owner 352 would be formatted as text as 00352 and in the new system it is a number as 352.

We are having to update our legacy system due to some issues that have happened so I am extracting owner information from the current database and trying to use vlookup to merge the data, however, there is a data mismatch and vlookup is returning #N/A.

I have gone into the custom formatting on the data from the new system and set it up as 00### which gives me the correct format, but I can't get excel to recognize it as text. It has to be text because that is what the legacy system needs to see when I upload the updated data back into it. Is there anyway to make this happen?

Thank you in advance.