you need to use legacy place converter and make sure before converting the file format is rbxlx not rbxl also (and this is very important) make sure any plugins that put stuff in the terrain or camera are disabled and if they have delete what they added as this caused problems for me it can also convert scripts (i think) but id make sure to check over as many of them as you can to make sure they are all compatible with said version of roblox link:
https://github.com/...r?tab=readme-ov-file (or open novetus go to sdk and use its legacy place converter)