Variable products in WooCommerce let you offer a set of variations on a product, with control over prices, stock, images, and more for each variation. For example, variations can be used for a product like a t-shirt, where you can offer large, medium, and small and in different colors. If you need at this link you can find the official guide:
Create variations from all attributes
If you are working with Variable Products, please note that it is recommended to set every possible combination in WooCommerce. To set proper variations, please create a variation for each combination of your product automatically using the Create variations from all attributes, screenshot .
Then use this option to automatically set each variation's price automatically, screenshot .