Making a place name “Mando”
We see in the original dictionary that Kaminoan, Jedi, and the Galactic Republic have different names, while "Jawa" and "Nikto" are the same. Likewise, we don’t have any large bodies of text entirely in Mando’a that deal with place names, so it’s impossible to say what in-universe Mandalorians do with the names of locations. The name "Coruscanta" appears in the songs, but this might be how the change it for the song (as they do with the pronunciation of some words), or maybe it was one of the Taung names for the planet, which is why it was adopted into Mando'a that way, while many other places names have no special significance to Mandos and thus no reason to have a special version for them.
If you want to give a story a Mando flair, adapt the name to use sounds that are common in Mando’a words. Otherwise, keep the name whatever you know the place name as.
According to a post from the original conlang author on boards.theforce.net: "Mando'ade tend to call other species and races by the names they use for themselves, if they can pronounce them. ... Their rationale is this; if that's what folks want to call themselves, who are we to argue? Of course, they then go on to use those names as shorthand descriptive forms in their own right, which isn't always flattering ... but that's Mando'ade for you."
We also know that Mandos don’t seem to change the names of people. Thus, it's simplest to keep the name of the city, planet, culture, title, personal name or whatever as whatever the specific thing's "official" name is.
This is a good video for understanding the sounds of Mando’a:
youtube.com/watch?v=-wRs65XyvHI