I tried the solution from unson1x without success. I then attempted to follow the instructions from Terza36, but searching for "windows.plist" in the containers folder resulted in 26 different windows.plist files.
For those who are not as tech-savvy, here is the exact pathway I took, following both the pathways mentioned by uson1x and Terza36.
Open the Finder >> press ALT(Option) >> Click GO in the very top bar menu >> select Libraries (without ALT(option) it will not appear).
From Libraries >> Search for "Safari" >> Click to open com.apple.Safari.savedState folder >> Delete the windows.plist file >> Open Safari
(Alternative long to find saved state folder: From Libraries >> Search for "Safari" >> Click to open com.apple.Safari >> Open Data folder >> Open Library Folder >> Open Saved Application State folder >> Open com.apple.Safari.savedState folder >> Delete the windows.plist file >> Open Safari)
This worked great for me. Hope it helps others out.