IRC means Internet Relay
Chat. mIRC is not the same as IRC, and mIRC is not a file transferring program. It is not a p2p program and shouldn't be used for that. Unfortunately people do, but when it involves mass/illegal file trading we don't help with it on this forum, nor do many help channels on IRC.
It's illegal a lot of the time, a good way to get a virus, the DCC protocol was never intended to deal with a) a large number of transfers at the same time, b) deal with particularly large files. The same goes for mIRC.
You may like to read
this post.
Regards,