Trouble with WHERE EXIST subquery of a LEFT JOIN - sql

Question

I am trying to run a Left Join in the MS Access SQL. I am trying to Left Join my "OldPE" table to New "1 PE" table and update my column labeled "Line Num". There is no primary key in these tables so I am linking them through a series of conditions. Here is my code so far (excuse the poor formatting I am new and still learning SQL).
UPDATE [1 PE]
LEFT JOIN OldPE ON ([1 PE].SumRes = OldPE.SumRes)
AND ([1 PE].[Project Code] = OldPE.[Project Code])
AND ([1 PE].[DeptID] = OldPE.[DeptID])
AND ([1 PE].[Res Code] = OldPe.[Res Code])
AND ([1 PE].[Explain The Cost] LIKE OldPE.[Explain The Cost])
AND ([1 PE].Notes LIKE OldPE.Notes)
SET [1 PE].[Line Num] = [OldPE].[Line Num];
There are a lot of rows that have null or blank values in their "Explain The Cost" and "Notes" columns. I used a like statement because some of the notes that I want together vary slightly due to spelling mistakes and such. However now that I use the "like" it won't return the rows with a null value for these columns. The SQL code wont accept a WHERE EXISTS (I may also just be writing it wrong).
How do I get these null values to still be returned while using the Like command

Answer 1

Use ISNULL to join back to the original value if it is null. (This will include the null values in the results.)
AND ([1 PE].[Explain The Cost] LIKE ISNULL(OldPE.[Explain The Cost],[1 PE].[Explain The Cost]))