can't open new tab in react, adds localhost:3000 on link?

try this

<Link target="_blank" to={"//www.mylink.com"} >mylink </Link>

or this

<a href={'//www.mylink.com'} target="_blank" > mylink </a>

for more reference:
Absolute vs relative URLs
https://en.wikipedia.org/wiki/Uniform_Resource_Identifier#Generic_syntax