Since you have the comma-separated row, it must be a single cell with text with separators. First, break the cell to individual cells by the separator; do that using the
Text to Columns command, and select the proper separator. Then you will have the actual row with cells holding the individual addresses.
To turn the row into a column (or “transpose”, which is the usual technical term), follow the instructions in this previous Q&A.
Once that is done, Select the column you wish to sort (e.g., by clicking the Column heading, A, or B, or whatever), then from the menu bar, Data > Sort… and set your choices (e.g., “Column A” with the Ascending radio button clicked).
There is then the matter of removing duplicates… You can do that manually (of course) but if you have a lot of data, that can be automated. I’ll either pick that up later, or someone else my add that in to another answer.