As variations are stock keeping units, you may wish to revert your variations back to basic options without individual stock keeping. You can do this within the product options area for just one product, or you can complete this as a bulk action for many products.
To do this, go to your options/sizes tab in the product which should take you to your variants.
On each variant, click the edit button on the right hand side.
Scroll down and click Convert variant to ordinary product.
You will need to do this for each variant that needs to be converted.
Press Publish when all changes are made.
Within your category, select all the products you want to remove the stock keeping variations from by checking the box next to them.
A new menu will appear on the right hand side of the CMS
Scroll down to the bottom and click Remove Variants. This converts the variants to "normal" options within the product.