Custom Modpack Error

[Gnardokk]

ive been doing research for about 2 hours now and im starting to give up i just installed a few mods so me and some friends could play together and it was working fine till i added some new ones i did research on the mods i downloaded and they seem to have no issues with any of my other ones the issue only happens when i right click and drag ive got 0 clue and im hoping someone here can help despite me being on 1.12.2 

[Ugdhar]

1.12 is no longer supported due to age.

Please update to a modern version if you wish to receive support here.

See the LTS link at the top of every page for more information on supported versions.