If you wanna move to 4.4.10 you need php 7.1 or higher but wit 7.1 its works great. Just copy the files of 4.4.10 in your forum directory ( do not copy conf_global ) and then go to /admin/upgrade and run the upgrade. But your theme will no longer work among with other plugins / apps you have on the 3.4.8 ! I can do a video tutorial if you want.