Joe common time is 4/4 or 4 quarter notes in each bar and is counted 1-2-3-4

3/4 has 3 quarter notes in each bar and is counted 1-2-3

6/8 has 6 eighth notes and is counted 1-2-3-4-5-6

If you clap those rhythms you will hear/feel the difference Sorry can't help with the others