Prakash,
Which version of MyEclipse are you switching from?
You can configure Tomcat 6 in MyEclipse 2017 using the connector available by right clicking in the Servers view > New > Server. Look for Tomcat, expand and select the Tomcat 6.x connector, point to the installation directory to define the server. Once done, the Tomcat 6 will be listed in the Servers view, double click on the entry to open the Overview page. You can change the working directory and other settings from the Overview page.
Hope this helps. Let us know if you see any issues.
–Swapna
Genuitec Support