I am already installed ubuntu 18.04 LTS and I want to remove it and change it to windows, but i have an important data where its so big size.
how to install windows 10 without losing my ubuntu data ?
please help me
Because Windows uses the NTFS file system and Linux uses the ext4 file system you'll have to copy/backup the data somewhere before re-installing.
Your options are:
Upload to the cloud such as Google Drive; or
Copy data to a USB disk or another external drive; or
Use the Live USB installer to resize your disk and create an extra NTFS or FAT32 partition and move your data to that partition and be careful not to allow Windows to format it when installing