For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/X11:lxde/openSUSE_Tumbleweed/X11:lxde.repo
zypper refresh
zypper install pcmanfm
For openSUSE Slowroll run the following as root:
zypper addrepo https://download.opensuse.org/repositories/X11:lxde/openSUSE_Slowroll/X11:lxde.repo
zypper refresh
zypper install pcmanfm
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/X11:lxde/15.4/X11:lxde.repo
zypper refresh
zypper install pcmanfm