Referral Traffic User Journeys

Hi, I have 2 websites. On Website A is a Brand Awareness campaign and Website B is a Lead Generation Campaign. My Paid Media is driving traffic to Website A. When users land on Website A they have to click a button for more information which directs them to Website B to either purchase or contact us. The problem i am having is that I can't attribute the users from Paid media (Website A) to a conversion on Website B. I can track the referrers tab but can't the user journey of the referrer? Is there a way to attribute Website A users to Website B Sales or Contact us submissions? Or how far into the User Journey can i track the referral users from Website A to Website B. The Referral URL contains a CSRef which we can use to identify but all i can see if the page that they landed on. I cant seem to find out if they lead to a sale or completed a form submission. Please can you advise how can I see this data on Website B.