Across Episode 1 and 2 of "The Mandalorian", it seems that there are three planets visited:
Planet 1: The planet where Din Djarin (The Mandalorian) captures Mythrol
Planet 2: The planet where he meets with Greef Karg to get the new bounty
Planet 3: The planet where he recovers the asset (answered: known to be Arvala-7)
Planet 2 where the Mandalorian meets with Greef Karga to get the bounty is revealed as Nevarro in Episode 5 "The Gunslinger" by Fennec Shand, "Ever been to Nevarro? I hear things didn't go so well there, but it looks like you got off easy."
Referencing the shootout in Episode 3 between the Mandalorians and the bounty hunters guild.
Edit: Thanks to Mithoron for the Wookieepedia article for Planet 1 that is now Identified as "Maldo Kries" in this article from American Cinematographer Magazine
