How to install High Sierra on older MacBook Pro

I have an older MacBook Pro (13-inch, Late 2011) that I tried to update to Mojave, however, I get a message that says the MacBook is too old. It is also at 10.10.5. Therefore, I'm trying to upgrade it to High Sierra, but when I search for HS at the APP Store, nothing comes up. Where can I get a copy of High Sierra?