Write this code in .htaccess file

# WordPress SEO – XML Sitemap Rewrite Fix
RewriteEngine On
RewriteBase /
RewriteRule ^sitemap_index.xml$ /index.php?sitemap=1 [L]
RewriteRule ^locations.kml$ /index.php?sitemap=wpseo_local_kml [L]
RewriteRule ^geo_sitemap.xml$ /index.php?sitemap=geo [L]
RewriteRule ^([^/]+?)-sitemap([0-9]+)?.xml$ /index.php?sitemap=$1&sitemap_n=$2 [L]
RewriteRule ^([a-z]+)?-?sitemap.xsl$ /index.php?xsl=$1 [L]
# END WordPress SEO – XML Sitemap Rewrite Fix