do you know of a free app (if not there is fine even paid) that allows me to do this?
thank you 
Hey Fluffyjoy,
If you’re looking for an app to provide this functionality, you’d probably want one of these: https://apps.shopify.com/search?q=quantity%20breaks
Another way to handle this though (which is 100% free) would be to setup “automatic discounts” for your store: https://help.shopify.com/en/manual/discounts/discount-types#automatic-discounts
You can set up the discounts so that if a customer purchases 2 socks in the same order, then it automatically applies a discount at checkout. You’d then just need to add a message somewhere on the site (or product page) letting your customers know about this discount (as it won’t tell them on product pages, like your screenshot does, by default).
Cheers,
Stephen