Magento 2 Converts Virtual Products To Simple Products

Step-1: By Using Magento 2 Admin,

• Go To Magento 2 Admin
• Catalog–Products: select Virtual Products, which you want to converts into simple products.

• Click on Edit

• Go To Weight: “The item has no weight” for Virtual Product already mentioned.
• To Converts into Simple Product, select Item has weight & put
  weight value.

• Finally Click on Save button & Virtual Product will be converted into Simple
  Product.

Step-2: By Using Database SQL Query

update catalog_product_entity 
set type_id = 'simple' 
where type_id = 'virtual'

Note: Be careful, this query will be converted all Simple Products To Virtual Products

Note: If user wants to convert specific Simple Products To Virtual Products, below query need to run

update catalog_product_entity 
set type_id = 'simple' 
where type_id = 'virtual' and sku in ('BSX55MOLCG','BSX55MOLCLW','BSX55MOLCMW','BSX55MOLWWH')