Convert string to const unsigned char for display

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String abc ="0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff"

const unsigned char displaydata[ ]={ '"+abc+"'}; (not working)

Is there a way to convert the string data into a const unsigned char variable or write it into the existing variable?