I’m trying to install tree on the SLES12 SP4 but message appear with SLES12 SP4 : package ‘tree’ not found.
Hi and welcome to the Forum 
It doesn’t look like tree is present in the release, there is pstree and mtree available from SUSE Package Hub.
I have an unsupported version built on OBS and available for download;
https://build.opensuse.org/package/show/home:malcolmlewis:SLE_12_General/tree
https://download.opensuse.org/repositories/home:/malcolmlewis:/SLE_12_General/SLE_12_SP4/x86_64/tree-1.8.0-27.1.x86_64.rpm