Error :- CV_RETR_EXTERNAL :- was not declared in the scope

cv::findContours(bw.clone(), contours, CV_RETR_EXTERNAL, CV_CHAIN_APPROX_SIMPLE); how to solve not declared in the scope error for CV_RETR_EXTERNAL, and CV_CHAIN_APPROX_SIMPLE

you’re looking at outdated samples / documentation

all those CV_ prefixes were dropped with 3.0 already