In regard to the topmost answer, using a bunch of if’s or a switch in order to convert a string to a number and then back to an enum is a really bad and unoptimized way of doing it.
enum EMyEnum
{
// ...
};
FString fsComboBoxValue = TEXT("1"); // Your combobox value
int32 iEnumValue = FCString::Atoi(*fsComboBoxValue);
EMyEnum myEnum = EMyEnum((uint8)iEnumValue);
If FCString is undefined you might need to include: Runtime/Core/Public/Misc/CString.h