Can we use Arduino mini in eagle to create new custom modal
From https://www.arduino.cc/en/Main/FAQ#toc8:

I want to design my own board, what should I do?
The reference designs for the Arduino boards are available from their specific product pages. They're licensed under a Creative Commons Attribution Share-Alike license, so you are free to use and adapt them for your own needs without asking permission or paying a fee.

You can find the board design files on the Documentation tab of each product page.
Arduino Mini product page:
https://store.arduino.cc/arduino-mini-05
Arduino Nano product page:
https://store.arduino.cc/arduino-nano