Hi Zahra, 

I am unsure how to execute in CONN but MRIQC (https://mriqc.readthedocs.io/en/latest/) can calculate DVARS, as well as several other IQMs. Of course, data must be in BIDS before MRIQC will be able to execute. Depending on where you are at in the process and the number of participants, this may be an easier option. Just a suggestion!

Cheers, 

Nick