When I export my activities I see a field named avg_stride_length. For walk activities it's .82 to .85 What does this number represent and can it be convert it to inches or feet and if so how?
What does this number represent
Stride length is the length of your stride from one footfall to the next, measured in meters. For watches and/or HRMs that support it.

can it be convert it to inches or feet and if so how?
I don't believe so in Garmin Connect Web. You could periodically do the conversion manually or in an Excel formula - multiply the length value by 39.37