For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/X11:xfce/openSUSE_Tumbleweed/X11:xfce.repo
zypper refresh
zypper install thunar-plugin-archive
For openSUSE Factory run the following as root:
zypper addrepo https://download.opensuse.org/repositories/X11:xfce/openSUSE_Factory/X11:xfce.repo
zypper refresh
zypper install thunar-plugin-archive
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/X11:xfce/15.6/X11:xfce.repo
zypper refresh
zypper install thunar-plugin-archive