SNMP Data Collection Issue - Extract and convert OID string type to integer

I am trying to collect data from an interface that returns the following SNMP data:
. = STRING: “43.45 degrees C normal”

The issue is that since the returned type is string, there is no .rjb file (rrd) created. Instead, this data is getting written to a file.

Expected outcome:
I want the float value (43.45) to be extracted and inserted in the RRD so that as a result, this interface data gets plotted on a graph.

OpenNMS version:

Other relevant data:
[e.g. logs from OpenNMS, error messages etc]