Generate sheet with lots of variation

[12Torquay12]

Good afternoon everyone, thank you for taking the time to look at this
Here is my issue, I need to upload my stock to our Shopify site.
The problem is it has to be in a specific format for it to work correctly
I have many 100's of t shirts that have variations as in
small medium large etc
black, white, navy blue etc
And each product has its own specific SKU, i.e.
3957 SML WHT
3957 MED WHT
3957 LG WHT
3957 XL WHT
3957 2XL WHT
3957 3XL WHT
3957 4XL WHT
3957 5XL WHT
As you can see the common denominator here is the text after the number, so the number 3957 with have many variations and all are different
On sheet 1 I have my numbers which are unique, can i generate on sheet 2 the corrosponding codes
I have attached a workbook with what i am looking for
Not sure if I managed to add an attachment...
Thank you
Kim

[JeteMc]

For this proposal to work lists of sizes and colors need to be produced in an abbreviated form as in column J of the Sheet to Upload.
The lists of SKU's, Sizes and Colors are shown in columns L:N on the Stock Numbers sheet.
S1:T1 display the number of items in the Sizes and Colors columns using: =COUNTA(M2:M18)
R1 displays the number of times each SKU should be shown using: =S1*T1
R2:R545 are populated with the SKU's using: =INDEX(L$2:L$18,ROUNDUP(ROWS(A$1:A1)/R$1,0))
S2:S545 are populated with the sizes using: =INDEX(M$2:M$18,IF(MOD(ROWS($A$1:$A1),S$1)=0,S$1,MOD(ROWS($A$1:$A1),S$1)))
T2:T545 are populated with the colors using: =INDEX(N$2:N$18,IF(MOD(ROUNDUP(ROWS(A$1:A1)/S$1,0),T$1)=0,T$1,MOD(ROUNDUP(ROWS(A$1:A1)/S$1,0),T$1)))
The Output column is populated using: =R2&" "&S2&" "&T2
Let us know if you have any questions.