Possible to find value in 1 column and paste over into another?

[ub3rm0nk3y]

I've tried researching myself but my knowledge of excel advanced methods are still out of my reach. I can copy and paste but I'm unfamiliar with how to write anything myself.
What I am trying to do is edit the information in column b. To explain it the easier way I know how would be to read Column A and compare it to column B. Select each box of Column B that matches A. So you see here Column B is a list ranging from 1-10. Let's say it goes from 1-1000 in order. In Column A I have 10 values that I want to find in Column B. Instead of scolling down through the list I was looking for a way to automate the selection.

If this is possible then I'll be much appreciative. If it's also possible to automatically rename those selecting boxes "tif" to "jpg" then that would be even more amazing. Thank you for even reading this.

DOCUMENTS-000021    IM,DOCUMENTS-000001,D,0,@Export;THNelsonClaim\IMG_0000001;DOCUMENTS-000001.tif;2,0 
DOCUMENTS-000036    IM,DOCUMENTS-000002,,0,@Export;THNelsonClaim\IMG_0000001;DOCUMENTS-000002.tif;2,0 
DOCUMENTS-000037    IM,DOCUMENTS-000003,,0,@Export;THNelsonClaim\IMG_0000001;DOCUMENTS-000003.tif;2,0 
DOCUMENTS-000039    IM,DOCUMENTS-000004,,0,@Export;THNelsonClaim\IMG_0000001;DOCUMENTS-000004.tif;2,0 
DOCUMENTS-000041    IM,DOCUMENTS-000005,,0,@Export;THNelsonClaim\IMG_0000001;DOCUMENTS-000005.tif;2,0 
DOCUMENTS-000042    IM,DOCUMENTS-000006,,0,@Export;THNelsonClaim\IMG_0000001;DOCUMENTS-000006.tif;2,0 
DOCUMENTS-000045    IM,DOCUMENTS-000007,,0,@Export;THNelsonClaim\IMG_0000001;DOCUMENTS-000007.tif;2,0 
DOCUMENTS-000046    IM,DOCUMENTS-000008,,0,@Export;THNelsonClaim\IMG_0000001;DOCUMENTS-000008.tif;2,0 
DOCUMENTS-000047    IM,DOCUMENTS-000009,,0,@Export;THNelsonClaim\IMG_0000001;DOCUMENTS-000009.tif;2,0 
DOCUMENTS-000048    IM,DOCUMENTS-000010,,0,@Export;THNelsonClaim\IMG_0000001;DOCUMENTS-000010.tif;2,0  

[protonLeah]

edit: deleted, location fixed.
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Post a workbook. the sample you posted isn't in Excel format, no one can tell what the columns are.
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[ub3rm0nk3y]

I wasn't aware it was public. Fixed. Thanks. Haha.

[ub3rm0nk3y]

Here is an excel file.

[ub3rm0nk3y]

With reference to the above excel. The end result I am trying to accomplish here is finding A1, B1, C1, etc in column B and renaming "tif;2,0" to "jpg;4,0".

[protonLeah]

column C:

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MATCH(MID(B36,4,15),A:A,0) looks down column A for the DOCUMENT-XXXXXX substring of column B. If the value is found, it returns the row number, else it returns #N/A.
If it returns #N/A, the ISNA() function is therefore, TRUE, so the IF results in "" (null or empty) in the cell. If MATCH returns a row number then ISNA is FALSE and the IF evaluates
SUBSTITUTE(B1,"tif;2","jpg;4") which simply replaces the tif... with jpg...

[ub3rm0nk3y]

You're beautiful. That's absolutely perfect. Thank you very much.