One month ago, I updated all the product URLs on my site which were separated by _ sign to be separated by - sign.
Example:
.com/Calipers/Insize_1108
now looks like
.com/Calipers/Insize-1108
There were nearly 1200 links updated, and it is showing in webmaster tools as crawl errors. I marked them as fixed, I resubmited my sitemap but it didn't work, they are still showing in google search results.
What should I do ?