The Book of Moses 1 speaks of God creating many worlds.
Visions of Moses, June 1830 [Moses 1], [2], The Joseph Smith Papers website, accessed February 23, 2023
For mine own purpose have I made these things here is wisdom & it remaineth in me & by the word of my power have I created them which is mine only begotten Son full of grace & truth & worlds without number have I created & I also created them for mine own purpose