Q1- Can you tell me like what this formula says means what you did ? Like have you done in any formula in monthly sheet too ?
When you make a new inventory month tab e.g insert a new row before the average column copy the following index & match formula in and change in the formula to your new tab name 30-06-18
=IFNA(INDEX('30-6-18'!$D$2:$D$607,MATCH('5 Month'!$A2,'30-6-18'!$A$2:$A$607,0)),"")
Q1- Can you tell me like what this formula says means what you did ? Like have you done in any formula in monthly sheet too ?
=IFNA - If the item is Not Available #N/A in 30-06-18 then leave a blank cell.
(INDEX('Lookup tab 30-6-18'!range $D$2:$D$607, and the get the quantity on hand value from column D
MATCH(from the 5 month tab find '5 Month'!"CE0003, lookup column A '30-6-18'!$A$2:$A$607,0)),"") this gives the row number of CE0003 to index
Quantity on hand in the 30-06-18 tab for CE0003 is 181. It doesn't matter what row this item appears in each tab as index & match is designed to find it and return the correct value.
Q3- Now if I want to put this value in another sheet in the front of same item code what formula i can use or thus index match can use, in another sheet there is no repetition of item code all the code are different.
What you need to make sure is that 1 of every item in your product list appears in the 5 month sheet so that index & match can work. No formulas are needed in your month sheets as they are you're lookup data only.