Sum formula when cell cantains alphabets too

[d3graph]

hi there

i am looking for a Sum formula when cell contains alphabets too

sample data

70 meters 71 meters 72 meters 73 meters 74 meters 75 meters 76 meters 77 meters 78 meters 79 meters 80 meters 81 meters

this data is entered in same column and one cell contains like 75 mtrs

please help