I have a dataset

df

$MMM
$MMM$`WEOAGG:2024-04`
                                       series_code
                                            <char>
   1:                           001.BCA.us_dollars
   2:                      001.BCA_NGDPD.pcent_gdp
   3:                            001.BF.us_dollars
   4:                           001.BFD.us_dollars
   5:                           001.BFF.us_dollars
  ---                                             
1660:                      998.TTTPCH.pcent_change
1661:           998.TXGM_D.us_dollars_idx_2000_100
1662: 998.TXGM_DPCH.us_dollars_annual_pcent_change
1663:                    998.TXG_RPCH.pcent_change
1664:                     998.TX_RPCH.pcent_change
                                                                                          series_name
                                                                                               <char>
   1:                                            World – Current account balance (BCA) – U.S. dollars
   2:                                    World – Current account balance (BCA_NGDPD) – Percent of GDP
   3:                                                World – Financial account balance – U.S. dollars
   4:                                                   World – Direct investment, net – U.S. dollars
   5:                                               World – Financial derivatives, net – U.S. dollars
  ---                                                                                                
1660:                                       European Union – Terms of trade of goods – Percent change
1661:          European Union – Export price of manufactures (TXGM_D) – U.S. dollars; index, 2000=100
1662: European Union – Export price of manufactures (TXGM_DPCH) – U.S. dollars; annual percent change
1663:                                    European Union – Volume of exports of goods – Percent change
1664:                       European Union – Volume of exports of goods and services – Percent change

where

str(df)
List of 1
 $ MMM:List of 1
  ..$ WEOAGG:2024-04:Classes ‘data.table’ and 'data.frame':     1664 obs. of  2 variables:
  .. ..$ series_code: chr [1:1664] "001.BCA.us_dollars" "001.BCA_NGDPD.pcent_gdp" "001.BF.us_dollars" "001.BFD.us_dollars" ...
  .. ..$ series_name: chr [1:1664] "World – Current account balance (BCA) – U.S. dollars" "World – Current account balance (BCA_NGDPD) – Percent of GDP" "World – Financial account balance – U.S. dollars" "World – Direct investment, net – U.S. dollars" ...
  .. ..- attr(*, ".internal.selfref")=<externalptr> 

My goal is to extract from “df” the variables “series_code” and “series_name” and put them in two columns, where the first will be “series_code” (that will start from 1,2,3…up to 1664) and as second column “series_name” (that will start from 1,2,3… up to 1664)
Is there a way to do that?