There’s never been an official Tor Browser on mobile. Until now. The stable release is slated for early 2019.
Until this announcement, if you were using tor in your phones, you might have bee using Orbot and Orfox. Now things are going to change. After the major update and redesign of Tor Browser for desktop version 8, which is based on Firefox 60, the Tor Project has released a mobile (android) version of Tor Browser.
Best of luck.