First of all, this guide was made possible through the help of Linux Mint Community Members like Orcus, Cannabis Indica, Two Dogs, and xmetal who provided me instructions and links. on how i could update my LMDE 3 "Cindy" 64bit Kernel.

NOTE: THERE IS A MORE UPDATED AND MORE COMPLETE INSTRUCTION ON HOW TO UPDATE YOUR KERNEL USING BACKPORTS FOR LMDDE 3 MADE BY ORCUS PLEASE VISIT HIS WEBSITE AT

https://www.orcus.de/main_workarounds/lmde_backports_kernels.htm

DISCLAIMER: The kernels in backports are not officially supported by The Linux Mint Team

These are the exact steps i went through, in updating my kernel.

STEP 1: Enable Debian Stretch Backports: (type this in your terminal)

echo "deb http://ftp.debian.org/debian stretch-backports main" | sudo tee -a /etc/apt/sources.list > /dev/null

STEP 2: upgrade installed packages to their newer versions in the backports-repo in order to be sure that dependencies will remain unbroken.

sudo apt-get -t stretch-backports upgrade

STEP 3: Double check to see if you can now browse updated kernels from the debian backports: it should now list all the latest kernel available from debian. if you can see updated kernels then you can close your terminal now. pull up your synaptics package manager and proceed to step 4

aptitude search linux-image

STEP 4: Installing the kernel (Pls do this using your synaptic Package manager): 

open your synaptics package manager, then go or click "sections>kernel and modules" then look for the following items and mark each one for installation

linux-image-4.19.0-0.bpo.2-amd64

linux-headers-4.19.0-0.bpo.2-amd64

One you've these two items for installation, click the "apply button" on top of your synaptics package manager. then wait for it to finish.

STEP 5: Update Your GRUB Bootloader (Pull up your terminal again):

sudo update-grub

STEP 6: Reboot Your Computer:

after rebooting your computer, fire up your terminal again and type "uname -r" and it should now show you your updated kernel which should be 4.19 something... Congratulations! you've successfully updated your LMDE 3 Cindy kernel! :)

ORIGINAL SOURCE FOR THE INSTRUCTION CAN BE FOUND AT: (just copy the url addresses to your browser if you want to double check)

https://www.orcus.de/main_workarounds/lmde_backports_kernels.htm

http://jensd.be/818/linux/install-a-newer-kernel-in-debian-9-stretch-stable

https://backports.debian.org/Instructions/