Hi @emadhassan ,
What is the problem with your speakers that makes you want to change them?
Here’s a link to a [https://www.youtube.com/watch?v=SjzjVwU456o|video] which shows the dis-assembly of a Toshiba Satellite C55-A5310. I realize that it is not your exact model but it should be close enough to be of some help.
At 5:28 minutes into the video you can see one of the speakers.
Here is a link to a [https://www.ebay.com/itm/Toshiba-Satellite-15-6-C55-A5100-OEM-Left-Right-Speaker-Set-Speakers-A1113-/323200359226|supplier] of replacement speakers.
It is not a recommendation to use them. It it to show you what they look like so that you can identify them more easily when you have opened the laptop. There are other suppliers of replacement speakers for your laptop online, that may suit you better. Just search for ''Toshiba Satellite C55-A5100 speakers'' to get results.