Android Question Applying the old sign key into the project for updating.

Hi everyone, i have an old project on market and currently, i wanted to update that, when i have uploaded that on market i have an error related to the current sign key is not equal to the latest one, but the market has given me the old sign key that is something like this: " {'5R:C4D:BB:93:3E:EE:9F:2B:5D:0D:33:4B:8A:7A:EC:'} " ,
unfortunately, i do not have a previous sign key file anymore i have that key as text, and my question is how i can apply this key to my project so i can update that with the same key.