It's really easy if you have the app on both devices.
Android: After signing in/creating a drop box account, there is a tab at the bottom labeled "files", tap on it and you should see options to upload photos/videos, create folders, upload files, scan documents, and take photos. Select the upload option that will work for your file type, then select the files you want to upload. Finally, tap the button to upload them.
Once you have them on Dropbox you can log into your Dropbox on any device to access them. If you really want to download them to your iPad instead of just using them on the cloud (which requires an internet connection), this link might be helpful in guiding you through that process:
https://readdle.com/documents/how-to-connect-cloud
Also, don't forget to connect to your wifi when you try to upload or download this many files.
Currently I'm using a Rubber tip pen to draw with but I suggest you buy a stylus
I provided an example below
https://www.amazon.com/gp/product/B0745BX4LG/ref=ox\_sc\_act\_title\_1?smid=A1YPG1DCUHHP1T&th=1