Syslog traffic

Hi !
I use Open WRT on a ubiquiti Edge Router X, and I need to log the traffic network of users. For be in accord with the french laws but I don't understand why I can't make it with syslog-ng
Before I used DDWRT on Linksys WRT54GL and the log are like this:

"2019-08-02 11:49:02 warning 10.1.1.1 user kernel ACCEPT IN=br0 OUT=vlan1 SRC=10.1.1.212 DST=41.213.178.191 LEN=60 TOS=0x00 PREC=0x00 TTL=127 ID=7668 DF PROTO=TCP SPT=62375 DPT=60982 SEQ=4021919203 ACK=0 WINDOW=17520 RES=0x00 SYN URGP=0 OPT (020405B4010303080101040201000000000 "

I need to make the same function on OPENWRT.
I just need recording the mac, ip source, and the destination.

I specify that on my old system, DDWRT sent the logs on a simple NAS network

Can you help me to realise it ?? Thank you in advance.

Math.

This looks like output from
iptables ... -j LOG

which is a firewall rule, but only for logging. Creating lot of data.

yes I quickly a big files ... But I have 1 to for log it.

Thank for your responce,
I will try to do something that works, I did not try iptables.
If you have any advice, I'm here.