How to set Variable Slot Message?

Hello,

I want to do the following process, can you help me with this?

I am sharing the sample message below in the message written by the user. I want to define some variables and send them to another api service after writing the user message on rasa and return the response to the user.

Sample message :

I want a 16GB laptop.

If we take the above message as an example, the 16gb property variable should be the laptop category variable and it should be sent to the API as category:laptop property:16gb.