To add to Adaneth's response, any mod for that matter is only available for Minecraft Java Edition. It is possible to use addons to circumvent this, but the content of such addons are often very limited.
To add on to these two peoples responses (very original opening I know :) ) Do not install any app or download anything onto your devices that say it gives you mods for PE. This feature is ONLY for Java. You can however buy addons on the Marketplace.