Freshmarketer doesn't provide you a direct option to download "All contacts" at once but If you would like to download All contacts rather than a list then you can achieve it with a help of simple workflow journey. Please follow the below steps to download "All contacts" from your Freshmarketer account
Create a segment with the following condition
Choose Contact Fields => Email => Is Not Empty (refer screenshot below) and select "Save & Apply"
Now create a Simple Workflow journey with the following configuration
Add a Trigger Block with a Segment that we created in a previous step and then use the Action block as "Add to List"
Now All the contacts will be added to the new list you created. Now you can export the "All contacts" list by navigating the lists => Export
Refer this helpdoc to know How to export a list in detail
You can download only 50K contacts at max, if your list has more than 50K contacts, please drop an email to the support at firstname.lastname@example.org