It would be grateful if you will post a code for controlling the speed of 2dc motor from nodemcu controlled from blynk app
Excuse me for being blunt, but we are not a code factory 
What have you tried, which hardware are you one, etc? These are all questions which need to answered first. “What have you tried” being the most important one.
I think the basic blynk sketch will work.
Just need to use the slider widget and configure it to control directly 2 of many pwm gpio of the nodemcu.
FYI, you are replying to a 10+ month old topic, please take note of the time/date stamps on posts (hover over them for details).
PS, you hook up a DC motor to a PWM pin and you end up with a dead PWM pin ;).
A motor controller and additional controller appropriate library/coding is generally required.
This concept has been discussed and examples available throughout this forum.