Minecraft Earth is no longer on the Google Playstore and so must be downloaded through a third party APK provider. Mojang decided to remove Minecraft Earth from the Google Playstore due to the game not being as popular as they had anticipated.
To play Minecraft Earth after 30th June 2021, you must download and install it through an APK. APK's are app installation files and are safe to install.
Please understand that Minecraft Earth may no longer work as intended as the game is no longer supported by Mojang.