Hi, and welcome to LQ
If you have used the official rpm package to install openldap, then you can do the following to get the default slapd.conf. Copy the openldap-x.y.z.rpm to /tmp (or any other convenient directory), go into that directory and run:
rpm2cpio openldap-x.y.z.rpm |cpio -ivd ./etc/opneldap/slapd.conf
It will extract the file under etc/opneldap/slapd.conf, so you can use it.
And make sure you make a backup of a file before editing it