For me the best option would be to save it as inches.
With the use of 2 functions you'll never know that you are saving in inches and you'll be able to make calculations and comparisons (is this longer than that or whatever).
What you'll need is a function that will multiply the feet by 12 and then add the inches (in order to save it to the db), and a function that will read the inches and will perform floor(inches/12) & "'" & ((inches - floor(inches/12))*12) & """
or something like that.
Dim Adapter As New OleDbDataAdapter
Dim Command As New OleDbCommand
Dim xFrom As String = dtpFrom.Value.ToString.Substring(0, dtpFrom.Value.ToString.IndexOf(" "))
Dim xTo As String = dtpTo.Value.ToString.Substring(0, dtpTo.Value.ToString.IndexOf(" "))
sqlQuery = MainQuery ...