There is a very useful website, which will give you a lot of information about your device at a quick glance: https://www.whatismybrowser.com/
What's my device model?
Do you still have the box that the device came in or the manual? All the details should be in there.
The model name is sometimes displayed when you switch on the device.
Look for menu options such as “Settings”, “Options”, “About device”, “Preferences”
If you find a product code (that is not the model name), try searching online for it
GSM Arena (http://www.gsmarena.com) has a huge database and options like “Phone finder” and “Tablet finder” to help you find your model.