do i need to backup my mac not pro to update from el capitan to high sierra?

Do i need to use time machine to backup my files and fata dacta data from my mac os x el caapitan i mac to high sierra 10.13 i think so i don't lose my data. is it possible to get my info, files and dstya data lost wit h with with the installation from el capitan to high sierre sierra and if yes wgat what are are the chances?