There are many web browsers which comes from official Debian Jessie 8 repositories such as Iceweasel, Konqueror to name just few. For all reasons and intentions you should be able to do any work required a web browser using Iceweasel the official Debian Firefox clone. However, if you insists on using Firefox web browser you can install it easily by using Linux Mint’s imports repository. First edit your /etc/apt/sources.list
file to include:
deb http://packages.linuxmint.com debian import
Update system repositories:
# apt-get update