If you delete a Dropbox account, all your data stored in Dropbox will be lost 30-60 days after deletion. So be sure to back up your data. on an external storage device or in another cloud service. Deleted data can only be restored to Dropbox if you have a work account, so your data will be permanently lost 30 days after deletion.
In principle, for Dropbox as for any alternative cloud provider used for backups, it is always advisable to respect the backup rule 321. Thus, you should make at least three copies or backups of your important private or business data, two of which should be on an external storage medium, and one in a protected remote location (such as a cloud).