Sunfire and Ic161 both make good points.

I'm not sure if speaking things into Alexa will automatically save it all in a text format for you. And if it does I am unsure of how good the format it for reading back. If not an alternative could something through Google or Siri. For example, use Google voice to add voice to text notes to Google Keep, or use Siri and voice command that assistant to convert your speech to text in the Notepad app. You can speak and it will translate it into writing for you, and they'll also be backed up on cloud storage in case you ever lose or break the device.