How can I split a splited field in AWK?

I'm developing a script that has to take a text file with the format: field1@field2@20200101133030@field4 and I need to convert it into a sql insert command. Well. The third field is a date. I have a script that converts the date into to_date('2020/01/01:13:30:30', 'yyyy/mm/dd:hh24:mi:ss'),

funcion(){
        echo $1 | nawk -v s1="\047" -v firstPart="to_date(" -v lastPart="yyyy/mm/dd:hh24:mi:ss" '
                {
                        print firstPart s1 substr($0,1,4) "/" substr($0,5,2) "/" substr($0,7,2)":"\
                        substr($0,9,2)":"substr($0,11,2)":"substr($0,13,2) s1 ", " s1\
                        lastPart s1 ")"
                }'
}

And I have another script that splits the whole line into a insert command:

createInsert(){
        echo $1 | awk -F'@' '{
        printf "INSERT INTO myTable VALUES (\x27%s\x27,\x27%s\x27,\x27%s\x27,\x27%s\x27,\x27%s\x27,\x27%s\x27,\x27%s\x27);",$1,$2,$3,$4,$5,$6,$7;print ""
        }'
}

That works OK. Output:

INSERT INTO myTable VALUES ('0000000','D00','20200901131010','20200917133115','20200917142400','20200923120401','N');

My issue is that I need to convert the $3, $4 and $5 fields using the function below. But I think that awk doesn't allow to call another function like

createInsert(){
        echo $1 | awk -F'@' '{
        printf "INSERT INTO myTable VALUES (\x27%s\x27,\x27%s\x27,\x27%s\x27,\x27%s\x27,\x27%s\x27,\x27%s\x27,\x27%s\x27);",$1,$2,**$(funcion $3)**,$4,$5,$6,$7;print ""
        }'
}

Is there any form to create One single method that splits the fields $3, 4 and 5 and does the same that the other functions does (create it into a toDate function)

Thank you, hope your answers.

SUMMARY: Input:

`"0000000@D01@000000@20200910103010@20200910111111@20200910100403@N@"` 

Output:

INSERT INTO myTable VALUES ('0000000','D01','000000','to_date('2020/09/10:10:30:10', 'yyyy/mm/dd:hh24:mi:ss')',''to_date('2020/09/11:11:11:11', 'yyyy/mm/dd:hh24:mi:ss')','to_date('2020/10/10:04:03', 'yyyy/mm/dd:hh24:mi:ss')','N');