mix ram on budget

I have a Dell Inspiron 5537 brought in 2014 that came with a 4GB DDR3L 1600MHz Samsung as stock. A few months ago, I upgraded to an additional 8GB DDR3L 1600MHz Hynix stick. (https://www.amazon.in/dp/B016Z5VB38/) I'm now planning to replace the 1TB WD HDD with a 1TB SSD (make & model undecided)...