How to format string to money
Convert the string to a decimal then divide it by 100 and apply the currency format string:
string.Format("{0:#.00}", Convert.ToDecimal(myMoneyString) / 100);
Edited to remove currency symbol as requested and convert to decimal instead.
you will need to convert it to a decimal first, then format it with money format.
EX:
decimal decimalMoneyValue = 1921.39m;
string formattedMoneyValue = String.Format("{0:C}", decimalMoneyValue);
a working example: https://dotnetfiddle.net/soxxuW