Switching to string based ordinals (first, second, third…) is difficult. You’re likely going to want to create a dictionary for this to provide longer term flexibility (unless there is a package I’m not aware of in which case you can use that).
Since I’m not sure which version of Dynamo you’re in, I’m sidestepping the issue of changing dictionary methods/types, and instead will provide two options for nested if statement for you to work with:
The top option replaces 01 with first, 02 with second, and so on. Note that I stopped at 10 because I didn’t feel like coding up every ordinal number in the world as written text.
The bottom option replaces 01 with 1st, 02 with 2nd, and 99 with 99th. This is obviously more flexible, easier to write up, and less space consuming (twenty second vs 22nd). Also of note: neither option takes into account basement floors. Following the logic in the options provided should get you what you need though.