Mapping option set values to other values in the same option set

Hello,

I have already asked this question in the forum and people have suggested various answers but I could not get the desired results.

I have an Option set named Activity Stage in Dynamics CRM 365.

It has got the following values: Discovery 0, Discovery 1 and Discovery 2.

Each of these values have associated opportunities with them.

I want to map the opportunities for Discovery 1 and Discovery 2 to Discovery 0.

I have tried doing it by using SSIS, Import/Export wizard, Bulk edit but haven't got the desired results.

Any suggestions on this please?

Thank you.