Hi KimD2018, once you have your new company data file created, see the blog entitled "Top 3 items to do when setting up a new company"

Generally, Sage 50 will export a text file separated by commas. To have this viewable and separated by cells in MS Excel, open Excel from the main icon, then go to File > Open and browse for the text file. You'll then get a prompt to select Comma delimited, see KB 15158 below for more instructions.
 
Sage 50 can import invoices in IMP format. Contact lists would import in a CSV file format. This would be a manual process unless a 3rd party integration has been created by a development Partner (search www.sagepss.com). If not, then see the links below:
 
How do I export and import Company records?
- Provides steps on exporting a sample CSV file, with field headings / formatting

Importing sales invoices and other transactions in .IMP format
- Provides more detail on field and header specifications*

How to import/export list of accounts, clients, vendors, employees, stock or projects?
- 10124 shows you Excel and the formatting of data for import of lists.

- 10105 is specifically about importing customer data
 
Sage Accounting (formerly known as Sage One) is much easier to work with for importing and exporting invoices / client data, and it can link to Sage 50 afterwards at the touch of a button. But you'd need a Sage 50cloud subscription! We've consolidated Sage 50cloud setup procedures in this blog.

Heads up that our Sage Accounting Network partners are usually the ones to guide clients with integrations and importing of data. Find one using the Sage Match site: https://app.sagematch.com/