Deserialize JSON

In response to a request for data, SQL Exec block sends me the following response
[{"avg_av_20m_a2":"39.7500000000000000"}]
I took the null element of the array, created a virtual model string:float, but the deserializer returns null. I tried to unpack it through string:string, but without success. How to use the data received in the specified format?

Problem solved. Topic closed