How can I see a member's marketing consent (GDPR)in Salesforce?

When General Data Protection Regulation (GDPR) is enabled on your audience, you can create marketing consent preferences. These can appear on signup forms and preference centers so your constituents can grant or remove consent. 

In Salesforce, you can view a member's consent values on their Member details, in the GDPR tab. Member details can be viewed from the Audience member list or our member component on their contact or lead record. (Layouts)

Note:

• Our integration can't update these settings directly; that is a limitation on the Mailchimp side.
• Mailchimp also doesn't update them when a contact subscribes or unsubscribes, unless the audience member themself uses a Mailchimp form that includes them. 
•  They can't be reported on in Salesforce, as accommodating Mailchimp's data mode would quickly use up a lot of storage and processing time in the sync. 

To configure GDPR in Mailchimp, please see GDPR in Mailchimp

More information on GDPR and our integration security: GDPR background