MKV is a container. Nothing more!!!
It’s like .avi, .flv, .mov, .mp4, .m2ts, .ts, or even .zip!
You can’t be even sure that it is 720p, 1080p/i, 576 or something else.
You don’t know if it is x264, xvid, wmv, vc1, divx3-6…
Because it’s… tada! ONLY A CONTAINER!!
And if you only get these files to look them and you don’t know what specs they contain, you shouldn’t ask to convert them. Because you got them from some suspicious sources.