Learn more about this change here.
For help regarding Aternos, we recommend you to visit our support center.
I want to Play a mod pack in aternos server.
The mod pack link is - https://www.curseforge.com/min…acks/dark-souls-simulator.
My question is can I install the whole mod pack or Do I have to go through every mod and install them 
And which software is better for this mod pack like forge ,fabric etc.
Thank you for your time. 
That modpack is not available on Aternos since it doesn't provide a server pack, so you can't install the entire modpack directly, you would have to install Forge software and the mods one by one manually.
sorry m8
its easer to just use plugins look for sum of thos
Which version should I pick?
version of what?
That's your choice, as the modpack is 1.16.5, you should use 1.16.5, of course
ye
I just logged in. How can I advertise my server?
