Convert String to number in Blockly

OH 3.3 on Raspi4
Hello, I am fighting my way with Blockly to retrieve temperatures from Fritz thermostates and do calculations with them (weighted temperature of a house with many thermostates).
So, the temperature is stored in a channel like 20 °C and I use string commands to just retrive the number part. But then it is still a string and for further calculations I need to have a number. How would I do the conversion from string to number? In my example below, the last block does not compute for obvious reasons.

… I found a way … . I there another one?

The Method shown above does not work well. Sometimes it needs multiplikation with 1 to get a number, sometimes it does not work at all, it is a bit of a gamble.
It works by setting the Item from Point to Measurement.
It would be great to a have String=Number function in Blockly (besides embedded scripts)