Just a helper method to get a conversion that is not functional, but can be used to compare This is primarily to
speed up generating conversions to determine if one already exists.
Simply extracts BigInteger out of string, but also handles it when there is decimals - should use isWhole number
to make sure, because this will throw an exception if not perfect
This method will do what it needs to do to go out, read, etcetera the information it has to return ConversionType
that if fully populated with the custom conversions
The internal mechanisms in the implementing class are unknown, but depending on how it works, this method should
always return the date that this data is accurate to.