SAP Retail How to Convert single articles to Variant of Generic article

We have existing  Single articles in system,

We want this single articles to convert in to Variant of Generic article

Gen article-

                Var-1      Want to replace with Single article

                Var-2

For single article we will maintain same merchandise category & Article type  as generic.

For single Article  In basic data will assign characteristic value so it will be like variant

Bust assigning this number in generic article variant TAB NOT possible as it is generated automatically.