insert windows 11 installation media cdrom/iso
Make sure the command below points to the proper drive letter(in this case D)
Dism /online /enable-feature /featurename:NetFX3 /All /Source:D:\sources\sxs /LimitAccess
https://www.makeuseof.com/how-to-fix-net-framework-35-installation-error-0x800f0950-in-windows-11/