In crochet what does it mean when it states_143 stitches

Hello, Joyce -

I am not familiar with the crochet stitch abbreviation "sn". Did you mis-read the abbreviation, perhaps? Or, maybe there is a typo in the crochet instructions.

There is the crochet stitch abbreviation "sh" which stands for "shell" - a shell stitch.

See this tutorial for the shell stitch:
https://www.thesprucecrafts.com/how-to-crochet-a-shell-stitch-979096

This is a link to a master list of crochet stitch abbreviations for North America:
https://www.craftyarncouncil.com/standards/crochet-abbreviations

I suggest you contact the source of the crochet instructions and verify if "sn" was meant or not.

Best wishes.

Usually it is best to perform each step as stated in the pattern. Close the Puff stitch (follow the instructions for closing the Puff stitch), then Chain 1.

Perhaps this will help:

How to Crochet Puff Stitch dummies

Crochet Puff Stitch Slow Motion Crochet

Puff Stitch crochet

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This video will probably help:

Crochet Front Post Treble Crochet FPtrc

To make the stitch on the back of the stitch, you would insert the hook from the back side of the project and work the treble stitch on the back.

How to Crochet Back Post Triple Treble Crochet Stitch

...

Video instructions.
Tunisian Crochet Pebble Stitch

Look at Best Answer at link below:

Hi Carol, you may find that the knitting community www.ravelry.com is helpful to you, lots of free patterns, yarn discussions and information shared between members and its free to join up.

also Youtube is a great source of knitting tutorials, there's several that come up when I searched Cluster Stitch Crochet Cluster Stitch Crochet Guru Stitch Guide

try these link for videos
and websites
crochet stitch dc2tog Bing Videos Double crochet two together dc2tog Crochet Stitch Glossary Crochet Me How To Make Double Crochet Decrease dc2tog

do you mean cluny crochet? this appears to be type of lacy edging that is complex enough you will need to be able to read a pattern. here's examples of cluny crochet edging
http://qualitysuresewingandfabric.com/cluny-crochet.html

there's a lot of good youtube demos
How to Crochet the Popcorn Stitch (Left-Handed)
http://www.youtube.com/watch?v=7jzXfqbAWak

or #10 How to work a popcorn stitch in crochet tutorial LEFT-HANDED
http://www.youtube.com/watch?v=3Eba4e-GSmw

Ok, so do what it says... put your next stitch in the 81st stitch of the previous row.

HDC=half double crochet.