Hello Monika,
As far as your requirement is concerned, i am attaching few .osd files of 4 QAM , 16 QAM and 64 QAM systems. I suggest you to go through these .osd files and see the trend how parameters are changed in each system starting from 4 QAM. There must be a definite pattern how symbol rate , sequence length and all other parameters are varied for each system. You can also check for the ITU-T standards for the parameters for these systems. I hope you find it useful.
Regards