All you need is the Lat/Lon converted to decimal format

There are 60 minutes in a degree and 60 seconds in a minute so it is just a bit of slightly fiddly maths

degrees + minutes/60 + seconds/3600

so N50 21' 15" becomes

50 + 21/60 + 15/3600 =
50 + 0.35 + 0.004166 =
50.354166

If your data is in "degrees and decimal minutes" format (N50 21.25) then the maths is even simpler

degrees + decimalminutes/60

50 + 21.25/60 =
50 + 0.354166

Remember that west and south are negative so add a minus sign to the result for them