Explore Lite 

If you only have one channel integration, then you can use Explore standard dashboard and choose Any channel to filter Instagram messages

you will need to utilize Explore Professional if you have more than one Channel integration. 

Explore Professional 

We filter by tags to report on Instagram tickets.

Go to Queries on the left panel and press New Query. Choose Support Dataset

In Metrics Add> Tickets

In Filters Add > Ticket Tags

Click Ticket tags filter

Search and select origin_direct and origin_story (2 default Instagramer tags)

After this, you see the total number of Instagram tickets. You can slice and dice data as a next step to get the required results.

e.g. you can check how many Instagram tickets were created every day:

If you choose Column visualization you will get a report like this one:

Please note you can add your own tags to Instagram tickets via triggers or in the app's  Account -> advanced settings.