To validate purchases from Meta ads using offline data, integrate offline conversion tracking with your Meta ad campaigns. This can be done by importing purchase data from your point-of-sale system or CRM into Meta's Offline Conversions tool. You'll need to match the offline sales data (like transaction ID, email, or phone number) with the data Meta collects from your campaigns, helping you measure the impact of Meta ads on actual sales. This process ensures that the offline conversions are attributed correctly to your ad campaigns.