In the expression you propose it seems you require the string to start with
011 rather than have it as an arbitrary substring.
So in my dialect of RegEx the expression would be
(0+1)*011(0+1)*010. By definition that would specify all strings of the form $u 011 v 010$ where $u,v$ are arbitrary. This means all those strings have
011 as subword and end in
We also have to explain the converse. That every string with that subword and suffix is covered by the expression. For that it suffices to note that
010 cannot overlap. So,
010 must come before
011. Which means it is of the form $u 011 v 010$.