See https://www.odoo.com/pricing

Can I easily switch from a hosted plan (Odoo Online) to an on-premise plan (Odoo Enterprise) or the other way around?

• When using Odoo Online (this is our name for Odoo Cloud, some also call it the SAAS version of Odoo), you can download a backup of your database at any time through the control center. You own your data! 

• Our cloud infrastructure runs on the latest version of Odoo with regular upgrades. On-premise users must use the latest stable version of Odoo. If you would like to switch from Odoo Online to Odoo On-Premise, the best time to make this change is immediately following the release of the newest stable version.

Note: This means that is is easy to migrate from Odoo Online 13.0 (Cloud/Saas) to Odoo.sh 13.0 but challenging to move from Odoo Online 13.1 (Cloud/Saas) to Odoo.sh 13.0.  Since the Duscaff database is Odoo Online 13.0 you should move BEFORE upgrading to Odoo Online 13.1. Note that with Odoo.sh there will be no 13.1 release as point updates are not delivered to this platform.

All of your data will move seamlessly - there will be no issues with linked documents or records.

Specific instructions for this process are available at (even though it mentions moving from on-premise to odoo.sh, the process is the same for online to odoo.sh)

https://www.odoo.com/forum/help-1/question/how-do-i-migrate-transfer-an-on-premise-database-to-odoo-sh-aka-enterprise-146464