How to code this powershell script?

Recently, my internet setting is changed from PPPop into DHCP, and following code in powershell script is no longer applied,  I would like to know on how to code and reset the connection for DHCP using powershell script. 

Does anyone have any suggestions?

Thanks in advance for any suggestions :>

For PPPop setting

if ((20,40,60,80,100) -contains $i)
  {
   rasdial ABC /disconnect
   Start-Sleep -Second 2
   rasdial ABC username password
  }

Thanks in advance for any suggestions