The model number of the Roku device is the important thing. You can find it written on the device or displayed under Settings->System->About. If it's on this list under "Legacy models", then it's almost certainly worth getting a new one. To link it to your new account you have to factory reset it, but you should do that if you're going to get rid of it anyway. Before you do, make a note of the old device's current Roku account. You can also find that under Settings->System->About. Log into that account at https://my.roku.com and make sure you don't have any current subscriptions that are being paid through Roku. Cancel them if you do. Factory resetting a device won't close the old account, so if you're going to abandon the old account, you may want to close it.
How do I factory reset my Roku® streaming device? | Official Roku Support
How to close your Roku® account | Official Roku Support
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