I tried left click, right click, shift clicking, ctrl clicking, alt clicking, none worked.
please help

click what

click on the dirt block

You are supposed to sieve dirt. The right clicking mechanic is usually added by the modpack through KubeJS scripts. I could include it in the mod at some point in the future.

you might want this mod

so how would I get stone/cobblestone now?

First thing first, you need to grow some trees, then craft a barrel & a wooden hammer. Hammer can crush wood to wood dust which can be put into barrel to get dirt.

then you shall craft a crook, use which to break leaves to get more samplings & silk worm. put silk worm on a leave may infect it. break a fully infected leave using crook may drop more silk worm & string.
craft some sieve frame & string mesh, put mesh into frame. sieving dirt will deop pebbles

you might need JEI to view recipes