Hi @Namrata16,
Thank you for your question.
You could start by trying a mould cleaner such as Selleys 750ml Rapid Mould Killer Remover. Apply it over the mould, let it sit for 30 seconds, then wipe it off with a damp cloth.
If you find this doesn't remove all of the mould, then it is likely that it has embedded itself in the silicone, in which case you should cut out the old silicone, treat the mould in the cavity and then replace the silicone.
Put on some gloves, long protective clothing, a mask and eye protection so you can safely use a utility knife to cut out the old silicone.
Once the silicone has been removed, spray the mould remover in the cavity, let it sit for 30 seconds, then wipe the mould away. It is important that you get rid of the mould before applying new silicone, otherwise it will grow back.
When you've cleaned everything up, use How To Silicone a Gap as a guide for replacing the silicone. You can use a white silicone such as this SikaSeal White Kitchen And Bathroom Silicone Sealant.
Let me know what you think and if you have further questions, please don't hesitate to ask.
Jacob
