This requires either using a library with custom text functions, or learning how to handle text strings in BYOND yourself.
If you wish to learn it, you should prepare for reading and experimenting and looking up the text procs in the DM Reference: findtext(), copytext(), cmptext(), lentext() (the more up-to-date version is length()), addtext() (may be replaced with the + operator), text() (may be replaced with embedded expressions, meaning like texts like "damage is [src.str - M.def]") etc. There are also more, but you're not going to use all of them anyway. But you should also read the entry for "text" in the DM Reference and a little of the related entries there.

If you want to use a library, you're going to need to download it, include it in your project, and read it's documentation. Deadron has a good Text Handling library.