Can someone help me to make this problem i have to read from keyboard a number maximum 9 digits and multiply them and the show the result, and i have to press enter to validate the entry

introdu_latime:
mov ah, 09h
mov dx, offset msg4
int 21h

mov si, offset latime
citire:
mov ah, 01h    
int 21h         
cmp al, 13      
je menu_loop     
mov [si], al   
inc si          
jmp citire

introdu_lungime:
mov ah, 09h
mov dx, offset msg3
int 21h

mov si, offset lungime
citire2:
mov ah, 01h    
int 21h         
cmp al, 13      
je menu_loop     
mov [si], al   
inc si          
jmp citire2

afiseaza_aria:
; Calculeaza perimetrul
mov eax, latime ; Aduna latimea cu ea insasi
imul lungime ; Aduna lungimea
mov perimetru, ax

; Converteste perimetrul la sir de caractere
mov si, 5
mov sir_nr[si], '$'

mov ax, perimetru

; Converteste perimetrul la sir de caractere
repeta_perimetru:
    mov dx, 0
    div imp
    add dl, '0'
    mov sir_nr[si], dl
    dec si
    cmp ax, 0
    jne repeta_perimetru

; Afiseaza sirul de caractere
mov ah, 09h
mov dx, offset msg5
int 21h

mov dx, offset sir_nr
int 21h

jmp menu_loop

this is the part of the code