Help! Arduino speed counter

#1

Hello there.
Currently I want to program an Arduino based robot (Just L298N with 2 motors and an encoder IR FC-03) using mblock to track line and send speed signal back by bluetooth
But when I google it, all Arduino (not mblock) tutorials use interrupt function to count speed
And I could not find a similar block in mBlock.
Can anyone help me with the speed counter problem?

#2

Describe in detail what kind of sensor and put a picture of the appearance and connectors for connections.

#3

Thanks but my problem is sorted, no need to use mblock anymore.