Note, this is not Hostinger support, just the forum for AMP, we can still help you, but curb your expectations accordingly.
You’ll need to get the server pack zip from the modpack page and use that. You just upload the mods using the web file manager or using SFTP.
You can either go and read Hostinger’s guides and watch their videos, or follow this guide here:
https://discourse.cubecoders.com/docs?topic=1822
And there’s a FAQ here:
https://discourse.cubecoders.com/t/forge-frequently-asked-questions/2982